Adjustable camera with belt tensioning apparatus

ABSTRACT

A camera assembly including first and second rotating members and a motor assembly defining a first axis and operably coupled to first rotating member to drivingly rotate first rotating member. A flexible member operably couples first and second rotating members such that rotation of first rotating member causes rotation of second rotating member. A camera is operably coupled to second rotating member such that rotation of second rotating member repositions camera. The motor assembly includes a flange having an outer circumference defining a plurality of teeth and bearing against a support surface. The outer circumference defines a radially variable distance from first axis such that rotation of outer circumference against support surface displaces first axis relative to second rotational member and thereby adjusts a tensional force in flexible member. At least one pawl mechanism is fixed relative to support surface and is engageable with outer circumference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to adjustable cameras and, moreparticularly, to pan, tilt, zoom cameras wherein a belt driving therotational movement of the camera about an axis can be easily andselectively tensioned.

2. Description of the Related Art

Pan-tilt-zoom (PTZ) surveillance camera assemblies commonly use steppermotors to affect the pan and tilt motion of the camera. Such assembliesoften include a timing belt operably coupling a small sprocket attachedto the motor shaft to a larger sprocket attached to the camera. Inoperation, the rotation of the motor shaft drives the rotation of thesmall sprocket. The rotation of the small sprocket, via the belt,affects the rotation of the larger sprocket and, thereby, the movementof the camera. However, tolerances of the camera assembly components mayvary from one assembly to the next. Such variances can produce cameraassemblies having a belt that is either too loose or too tight. Beltsthat are too loose may produce hysteresis or slippage that adverselyaffects preposition accuracy of the camera assembly. Furthermore, aloose belt may shift entirely out of engagement with one or both of thesprockets, thus causing a failure of the assembly. If the belt is tootight, it can be difficult or impossible to assemble and attempts toassemble the belt drive may result in damage to the belt or othercomponents. If assembled, the overly tight belt may induce prematurewear of the belt or other components due to excessive forces generatedby the overtightened belt.

Some known camera assemblies include a means for selectively adjustingthe tension of the belt during assembly to thereby provide the properbelt tension. For instance, dome cameras, available from Bosch SecuritySystems, Inc. having a place of business at Fairport, N.Y., U.S., areknown to use the tilt assembly 10 shown in FIG. 1. The assembly 10includes a plate 11 having a first opening 12, through which a firstrotating member 15 is received, and a second larger opening 13 forreceiving a second rotating member (not shown). A motor assembly 14 isengaged to the first rotating member 15 and is mounted to the plate 11using screws 16, 17. A belt (not shown) operably couples the firstrotating member 15 to the second rotating member. To adjust the tensionof the belt, the motor assembly 14 is pivoted about pivot screw 16, thuscausing the first rotating member 15 to move within first opening 12 andtoward or away from second opening 13. Securing screws 17 slide withinadjustment slots 18 during pivoting of the motor assembly and aresubsequently tightened to secure the motor assembly in position.Although the Bosch dome camera provides an effective means forselectively adjusting the tension of the belt, the use of pivot screw 16and securing screws 17 presents additional loose hardware that must beassembled.

Pelco dome cameras, available from Pelco, Orangeburg, N.Y., U.S., areknown to use the tilt assembly 19 shown in FIG. 2. Tilt assembly 19includes a plate 20, a motor assembly 21 rotatably mounted in a pocketdefined at one end of the plate 20, and a tilt bearing 24 rotatablymounted at the opposite end of the plate 20. A belt (not shown) ispositioned on the underside of the plate 20 and connects the rotatingmembers (not shown) of motor assembly 21 and tilt bearing 24. Motorassembly 21 includes an eccentric cam portion 22 and a tab 23. A captivelocking screw 25 is provided that engages tab 23. As captive lockingscrew 25 is adjusted, it moves tab 23 causing motor assembly to rotatewithin the pocket of plate 20. As the motor assembly 21 rotates in thepocket, eccentric cam portion 22 engages the wall of the pocket causingthe motor 21 to move toward or away from the tilt bearing 24, therebytightening the belt.

Although the known systems provide for the selective tensioning of abelt drive system for a PTZ camera, an improved assembly is desirable.

SUMMARY OF THE INVENTION

The present invention provides a camera assembly having a belt drivecapable of being easily and selectively tensioned.

The camera assembly, in one form, includes a first rotating member, asecond rotating member, and a motor assembly operably coupled to thefirst rotating member and defining a first axis. The motor assemblydrivingly rotates the first rotating member. A flexible member operablycouples the first and second rotating members such that the rotation ofthe first rotating member causes rotation of the second rotating memberthrough the flexible member. A camera is operably coupled to the secondrotating member such that rotation of the second rotating memberrepositions the camera. The motor assembly includes a flange having anouter circumference defining a plurality of teeth. The outercircumference bears against a support surface. The outer circumferencedefines a radially variable distance from the first axis defined by thefirst rotating member such that the rotation of the outer circumferenceagainst the support surface displaces the first axis relative to thesecond rotational member and thereby adjusts a tensional force in theflexible member. At least one pawl mechanism is fixed relative to thesupport surface and is engageable with the outer circumference such thatthe engagement of the pawl mechanism with the outer circumferenceprevents relative rotational motion between the outer circumference andthe support surface in a first rotational direction.

The present invention also provides a method of tensioning a flexiblemember for repositioning a camera. In one form, the method includesproviding a camera, providing a motor, and operably coupling the motorand the camera with a belt drive assembly. The belt drive assemblyincludes a flexible member operably coupling a first rotatable memberand a second rotatable member. The method also includes tensioning theflexible member by adjusting the position of the first rotatable memberrelative to the second rotatable member and securing the first rotatablemember in a desired position by engaging a toothed surface with a pawlmechanism. One of the toothed surfaces and the pawl mechanism is fixedrelative to an axis of rotation of the first rotatable member.

An advantage of the present invention is that it provides a means foreasily and selectively adjusting the tension of the flexible member.

Another advantage of the present invention is that the pawl mechanismmay be integrally formed with a base plate in a molding operationwhereby the number of parts and assembly time required to provide thetensioning mechanism is minimized.

Another advantage is that the toothed surface, in cooperation with thepawl, provides numerous rotational positions for fine adjustment of thetension.

Other advantages of the present invention will become apparent byreferencing the detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The above mentioned and other features and objects of this invention,and the manner of attaining them, will become more apparent and theinvention itself will be better understood by reference to the followingdescription of embodiments of the invention taken in conjunction withthe accompanying drawings, wherein:

FIG. 1 is a top view of a prior art camera tilt assembly;

FIG. 2 is a bottom view of another prior art camera tilt assembly;

FIG. 3 is a top perspective view of camera tilt assembly according toone embodiment of the present invention;

FIG. 4 is a bottom perspective view of the camera tilt assembly of FIG.3;

FIG. 5 is a bottom view of the motor assembly of a tilt assemblyaccording to another embodiment of the present invention;

FIG. 6 a is a bottom view of a tilt assembly according to anotherembodiment of the present invention wherein the motor assembly is in afirst position; and

FIG. 6 b is a bottom view of the tilt assembly of FIG. 6 a wherein themotor assembly is in a second position.

Corresponding reference characters indicate corresponding partsthroughout the several views. Although the exemplification set outherein illustrates embodiments of the invention, in several forms, theembodiments disclosed below are not intended to be exhaustive or to beconstrued as limiting the scope of the invention to the precise formsdisclosed.

DESCRIPTION OF THE PRESENT INVENTION

Referring first to FIGS. 3 and 4, camera tilt assembly 30 includes amounting plate 32 defining a first side 34 and an opposite second side36. Mounting plate 32 defines first and second substantially circularopenings 38, 40 extending through plate 32 from first side 34 to secondside 36. Referring particularly to FIG. 3, a first rotating member 41extends through first opening 38 and is rotatable about a first axis A₁.First rotating member 41 includes a shaft 55 and a gear portion 42.Rotating member 41 extends through first opening 38 and projectsoutwardly relative to second side 36 of mounting plate 32.

Referring back to FIGS. 3 and 4, tilt bearing 43 is rotatably secured insecond opening 40 and a second rotating member 44 is coupled to tiltbearing 43, such that gear portion 45 of second rotating member 44 ispositioned on second side 36 of mounting plate 32. Second rotatingmember 44 includes camera bracket 47 to which a camera 49 (schematicallydepicted in FIG. 4) may be mounted. Referring specifically to FIG. 3, aflexible member 46, such as a belt, operably couples gear portion 42 offirst rotating member 41 to gear portion 45 of second rotating member44, such that the rotation of first rotating member 41 affects therotation of second rotating member 44. The gear portions 42, 45 ofrotating members 41, 44 may have discrete teeth which engagecorresponding teeth on flexible member 46 whereby the flexible member46, e.g., a belt, may positively engage the first and second rotatingmembers 41, 44 in a manner which minimizes potential slipping betweenflexible member 46 and members 41, 44. Such geared belts are well knownto those having ordinary skill in the art.

Referring now to FIG. 4, first side 34 of mounting plate 32 includes asubstantially circular recess 48 defined by a sidewall 50 which includesa support surface 52. As illustrated in FIGS. 3 and 4, a motor assembly54 is mounted on first side 34 of mounting plate 32. Motor assemblydefines an axis A_(m) about which the motor shaft rotates. In theillustrated embodiment, first rotating member 41 is operably engaged tothe motor shaft 55 of motor assembly 54, such that motor axis A_(m) isconcentric with first axis A₁. Motor assembly 54 includes motor housing56, which defines an eccentric flange 58. Flange 58 is disposed withinrecess 48, and retaining tabs 77 are provided to retain flange 58 inrecess 48 and prevent flange 58 from moving in a direction parallel tomotor axis A_(m). Flange 58 defines an outer circumference 60 whichbears against support surface 52 of sidewall 50. Although the first axisA₁ and the motor axis A_(m) are colinear in the disclosed embodiment,alternative configurations, e.g., where the axes are parallel and spacedapart, may also be employed with the present invention.

Referring now to FIG. 5, outer circumference 60 of eccentric flange 58defines a radially variable distance from first axis A₁ which, in theillustrated embodiment is colinear with motor axis A_(m). For example,as illustrated in FIG. 5, the radial distance R₁ is greater than theradial distance R₂. The radial distance of outer circumference 60decreases moving clockwise from distance R₁ to distance R₂ and increasesmoving clockwise from distance R₂ to distance R₁. Referring still toFIG. 6, outer circumference 60 defines a plurality of teeth 62 which areformed by a repeating set of surfaces. Each set of surfaces includes, incircumferential order, camming surface 68, bearing surface 70 andlatching surface 72. Camming surface 68 extends both circumferentiallyabout and radially outward from first axis A₁ (and motor axis A_(m)) toprovide a surface that slopes upward toward bearing surface 70. Bearingsurface 70 of outer circumference 60 extends circumferentially aboutfirst axis A₁ (and motor axis A_(m)) to provide a surface that issubstantially complementary to sidewall 50 and can bear flushly againstsupport surface 52. Unlike relatively sharp teeth that would bearagainst sidewall 50 in a series of line contacts, the extendingcircumferential length of individual bearing surfaces 70 distributes theforce exerted by outer circumference 60 over a larger area of sidewall50. As a result, the localized stress on sidewall 50 is reduced andteeth 62 are less likely to cut into sidewall 50. If the teeth were tocut into sidewall 50 due to the tension of belt 46, the first axis A₁would shift towards second axis A₂ resulting in the lessening of thetension in belt 46. Latching surface 78 extends radially from first axisA₁ (and motor axis A_(m)). The circumferential extending length ofbearing surfaces 70, however, may increase the distance between adjacentlatching surfaces 78 which can result in a greater increment betweenlatched positions. As described in greater detail below, the illustratedembodiment includes two pawl mechanisms for engagement with surfaces 78which are positioned to reduce the incremental distance betweensequential latching positions.

As shown in FIGS. 4, 6 a and 6 b, a pair of cantilevered pawl mechanisms64, 66 are fixed to support surface 52 and are configured to engagelatching surface 72 of teeth 62. Pawl mechanisms 64, 66 are biasedradially inward such that they bear against outer perimeter 60 of flange58. In the illustrated example, the pawl mechanisms 64, 66 each includean attachment location (e.g., 64 a) which unites the pawl mechanism withthe remainder of plate 32 and about which the remainder of the pawlmechanism may flex. The pawl mechanisms 64, 66 have a length that freelyextends from the integral hinge and which has a generally “L” shapedconfiguration. The longer section (e.g., 64 b) of the pawl mechanismshas a slightly arcuate shape to conform with sidewall 50 and the distalshorter section (e.g., 64 c) of the extending “L” forms a latchingportion that is engageable with a latching surface 78 to prevent therotation of flange 58 in one direction. The interaction of the L-shapedpawl mechanisms 64, 66 with teeth 62 of flange 58 allows for the one-wayratcheting rotation of flange 58 against sidewall 50 which allows pawlmechanisms 64, 66 to ride up and over the teeth when the flange isrotated so that the pawl mechanisms encounter camming surface 68,bearing surface 70 and latching surface 72 in that order but wherein thepawl mechanisms engage latching surface 72 to prevent rotation whenflange 58 is rotated in the opposite direction.

Flexible member 46 exerts two main types of forces on motor 54. Thefirst is due to the tension in member 46 and generates a force vectorthat is directed along the line extending between first axis A₁ andsecond axis first axis A₂. This force may be balanced by an equal andopposite bearing force transferred between flange 58 and sidewall 50.The other force exerted by flexible member 46 is a torque generatedduring operation of the motor. This force may be balanced by forcestransferred between pawl mechanisms 64, 66 and latching surfaces 72 thatare directed normal to a radial line extending from first axis A₁. Inalternative embodiments, pawl mechanisms 64, 66 may also be placed sothat the forces transferred between the pawl mechanisms and latchingsurfaces 72 are oriented substantially perpendicular to the forcestransferred between flange 58 and sidewall 50 to minimize thepossibility of inadvertently overloading the pawl mechanisms bytightening flexible member 46. Tabs 77 also restrain flange 58 andaccount for the axial separation between the two torque forces.

In operation, motor assembly 54 rotates motor shaft 55 about motor axisA_(m), which in turn rotates first rotating member 41 about axis A₁. Therotation of first rotating member 41, through the engagement betweengear portion 42 and gear portion 45 by flexible member 46, causes therotation of second rotating member 44. The rotation of second rotatingmember 44 affects the tilting of camera 49 which is rotatably supportedby tilt bearing 43. Tilting generally refers to the rotational movementof a camera about a horizontally disposed axis. In other words, wheninstalled axis A₂ would have a horizontal orientation. The presentinvention, however, may also be used to provide panning movement of thecamera wherein the rotational axis is vertically oriented, or, therotational movement of the camera about an axis having an alternativeorientation.

In order to achieve the smooth translation of rotational movementbetween first and second rotating members 41, 44, flexible member 46should have the proper tension. Referring to FIGS. 6 a and 6 b, thetension of flexible member 46 is easily and selectively adjusted byrotating motor assembly 14. More particularly, motor assembly 54 isrotated about motor axis A₁ in a direction opposite the rotation of themotor shaft. As motor assembly 54 is rotated, bearing support surfaces70 of flange 58 bear against support surface 52 of sidewall 50. Due tothe radially variable distance between motor axis A_(m) and bearingsupport surfaces 70, as flange 58 rotates within recess 48, motor axisA_(m) is displaced relative to axis A₂ of second rotating member 44.

For instance, in FIG. 6 a eccentric flange 58 is rotated to the positionwherein the shortest radial distance R₂ lies along a line connectingmotor axis A_(M) with second axis A₂. In this position, first axis A₁(and in the illustrated embodiment motor axis A_(M)) is located at itsclosest position relative to second axis A₂. In this position, flexiblemember 46 (FIG. 3) may be assembled around gear portions 42, 45 withminimal stress on flexible member 46 and first and second rotatingmembers 42, 44. Once flexible member 46 is installed, the tension may beadjusted to the proper level by rotating motor assembly. For instance,motor assembly 54 may be rotated to the position shown in FIG. 6 b,wherein a longer radial distance R₂ lies along a line connecting firstaxis A₁ with second axis A₂. In this position, first axis A₁ (and alsomotor axis A_(M)) is displaced to its furthest position relative tosecond axis A₂ and flexible member 46 is tensioned to its tightestlevel. Of course, motor assembly 54 need not be rotated to the point inFIG. 6 b. Rather, motor assembly 54 may be rotated to any position atwhich flexible member 46 reaches its proper tension. Such position mayvary depending on the exact dimensions of the tilt assembly components.

Referring to FIGS. 6 a and 6 b, flange 58 may be locked in position byeither of pawls 64, 66, which engage latching surface 72 to preventrotation of motor assembly 14 in the direction of the motor shaft. Asflange 58 is rotated within recess 48, pawls 44, 46 slide up cammingsurface 68 deflecting away from motor axis A_(m), slide across bearingsurface 70, and snap into engagement with latching surface 72. As aresult, teeth 62 provide a number of rotational positions in whichflange 58 may be secured. In addition, teeth 62 and/or pawls 64, 66 maybe in a staggered arrangement such that when one pawl 64 is inengagement with latching surface 72, the other pawl 66 bears againstbearing surface 70, as shown in FIG. 6 a. Further rotation of flange 58results in pawl 64 bearing against bearing surface 70, and pawl 66 beingin engagement with latch surface 72, as shown in FIG. 6 b. Such astaggered arrangement increases the number of possible rotationalpositions in which flange 58 may be secured and allows for a fineradjustment of the tension in flexible member 46.

Referring back to FIGS. 4 and 5, to facilitate the rotation of flange58, motor housing 56 may define one or more engagement features. In theillustrated embodiment, a collar 75 axially extending from flange 58includes engagement features 74 that take the form of two substantiallyplanar and parallel surfaces disposed on opposite sides of axis A₁ andwhich may be engaged by a wrench. In the illustrated embodiment, collar75 and engagement features 74 are integrally molded with motor housing56, such that motor housing 56 and engagement features 74 are formedtogether as a single integral unit. Alternative forms of engagementfeatures that can be engaged to affect the rotation of flange 58 mayalso be employed with the present invention.

To minimize the number of parts, the present invention contemplates thatpawls 44, 46 may be integrally molded with mounting plate 32. In otherwords, mounting plate 32 may be molded to include recess 48, sidewall50, support surface 52 and pawls 44, 46, such that mounting plate 32 isformed as a single unit including these features. Mounting plate 32 maybe formed of any material permitting the necessary deflection of pawls44, 46, such as a polymeric material. The illustrated embodiment, forexample, may be molded using a polycarbonate material having between 10and 20% glass fill, however, alternative materials and manufacturingmethods may also be employed with the present invention. For example,pawls 44, 46 may be welded onto or machined into plate 32 or on motorhousing 56 (with ratchet teeth being disposed on plate 32) and/or may beformed of a material, such as spring steel, different from that of theplate or housing and attached thereto. It should also be understoodthat, although the illustrated embodiments show a tilt assembly havingtwo pawls, the present invention is also effective when having only asingle pawl or more than two pawls.

While this invention has been described as having an exemplary design,the present invention may be further modified within the spirit andscope of this disclosure. This application is therefore intended tocover any variations, uses, or adaptations of the invention using itsgeneral principles.

1. A camera assembly comprising: a first rotating member and a secondrotating member; a motor assembly operably coupled to said firstrotating member and defining a first axis wherein said motor assemblydrivingly rotates said first rotating member; a flexible member operablycoupling said first and second rotating members wherein rotation of saidfirst rotating member causes rotation of said second rotating memberthrough said flexible member; a camera operably coupled to said secondrotating member wherein rotation of said second rotating memberrepositions said camera; wherein said motor assembly includes a flangehaving an outer circumference defining a plurality of teeth, said outercircumference bearing against a support surface, said outercircumference defining a radially variable distance from said first axisdefined by said first rotating member wherein rotation of said outercircumference against said support surface displaces said first axisrelative to said second rotational member and thereby adjusts atensional force in said flexible member; and at least one pawl mechanismfixed relative to said support surface and engageable with said outercircumference wherein engagement of said pawl mechanism with said outercircumference prevents relative rotational motion between said outercircumference and said support surface in a first rotational direction.2. The camera assembly of claim 1 wherein said support surface isdefined by a mounting plate, said mounting plate having a recess with asidewall, said flange being disposed within said recess and said supportsurface being defined by said sidewall.
 3. The camera assembly of claim2 wherein said recess defines a substantially circular opening.
 4. Thecamera assembly of claim 2 wherein said mounting plate comprises apolymeric material and said at least one pawl mechanism is integrallyformed with said mounting plate.
 5. The camera assembly of claim 1including at least two pawl mechanisms fixed relative to said supportsurface and engageable with said outer circumference wherein engagementof either of said pawl mechanisms with said outer circumference preventsrelative rotational motion between said outer circumference and saidsupport surface in said first rotational direction and wherein said atleast two pawl mechanisms engage said outer circumference at differentrelative rotational positions of said flange and said support surface,each of said different relative rotational positions of said flange andsaid support surface defining a different distance between said firstand second rotating members.
 6. The camera assembly of claim 5 whereinsaid teeth disposed on said outer circumference each define a latchingsurface engageable with one of said pawl mechanisms, said latchingsurfaces being spaced apart by variable circumferential distances. 7.The camera assembly of claim 1 wherein said outer circumference issubstantially defined by a repeating set of surfaces, each set ofsurfaces including, in circumferential order, (1) a camming surfaceextending both circumferentially and radially and wherein said cammingsurface radially biases said pawl mechanism as said flange is rotatedrelative to said support surface when said pawl mechanism is engagedwith said camming surface, (2) a bearing surface extending at leastcircumferentially, said bearing surface bearingly engaging said supportsurface along a circumferential length wherein an area of bearingcontact greater than a line contact is provided by said bearing surface,and (3) a latching surface extending at least radially and engageablewith said pawl mechanism to prevent relative rotational motion betweensaid outer circumference and said support surface in said firstrotational direction and allows relative rotational motion in anopposite second rotational direction.
 8. The camera assembly of claim 7wherein said bearing surfaces define a plurality of differentcircumferential lengths and said latching surfaces are spaced apart byvariable circumferential distances.
 9. The camera assembly of claim 7wherein said bearing surfaces are disposed at variable radial distancesfrom said first axis.
 10. The camera assembly of claim 7 wherein thetension is said flexible member is substantially balanced by a forcetransferred between said bearing surfaces and said support surface. 11.The camera assembly of claim 7 wherein a torque generated by operationof said motor and rotational driving of said first rotating member issubstantially balanced by a force transferred between said at least onepawl mechanism and a respective at least one latching surface.
 12. Thecamera assembly of claim 1 wherein said flexible member engages saidsecond rotating member to define a radius that is greater than a radiusdefined by the engagement of said flexible member and said firstrotating member.
 13. The camera assembly of claim 1 wherein said motorassembly includes a motor shaft defining said first axis and said firstrotating member comprises a gear member mounted on said motor shaft. 14.The camera assembly of claim 1 further comprising a mounting plate, saidmounting plate having a recess with a sidewall, said flange beingdisposed within said recess and said support surface being defined bysaid sidewall, said second rotating member being rotatably mounted onsaid mounting plate.
 15. The camera assembly of claim 1 wherein saidmotor assembly includes an engagement feature for rotating motorassembly relative to said support surface to thereby adjust the tensionin said flexible member.
 16. The camera assembly of claim 15 whereinsaid engagement feature is defined by two substantially planar surfacesdisposed on opposite sides of said first axis and spaced apart by adistance wherein said two substantially planar surfaces are engageableby a wrench.
 17. A method of tensioning a flexible member forrepositioning a camera; said method comprising: providing a camera;providing a motor; operably coupling the motor and the camera with abelt drive assembly, the belt drive assembly including a flexible memberoperably coupling a first rotatable member and a second rotatablemember; and tensioning the flexible member by adjusting the position ofthe first rotatable member relative to the second rotatable member andsecuring the first rotatable member in a desired position by engaging atoothed surface with a pawl mechanism, one of said toothed surface andsaid pawl mechanism being fixed relative to an axis of rotation of saidfirst rotatable member.
 18. The method of claim 17 wherein said motorhas a housing including a flange defining the toothed surface.
 19. Themethod of claim 18 further comprising the step of positioning the flangein a recess defined by a mounting plate and wherein said step oftensioning the flexible member includes rotating the flange within therecess.